1. Field of the Invention
The invention relates generally to the field of cellular radiotelephone systems, and more specifically provides a new mechanism for dividing cellular radiotelephone channels into diverse groups.
2. Description of the Prior Art
Cellular radiotelephone systems have recently been introduced in a number of areas to provide telephone coverage for people who need to have access to telephones from outside of their offices or are otherwise unable to get to telephones that are directly connected to a central office over conventional telephone lines.
In cellular radiotelephone systems, an area is divided into a plurality of small regions, or "cells", each of which is covered by a relatively low-power transmitter. Currently, cellular radiotelephone service is provided in the 825 to 845 Mhz and 870 to 890 Mhz frequency bands. The higher-frequency band is used for "down-link" transmissions from the "cell site" for reception by the subscriber. The cell site is the location of the transmitter, or, more specifically, the location of the antenna from which transmissions are effected for the cell. The lower frequency band is used for "up-link" transmissions from the subscriber in the cell for reception by the receiving equipment which is also located at the cell site.
Each frequency band assigned to the cellular radiotelephone system is divided into two groups, with one group being reserved for the local telephone company and the other group being franchised to a completing service provider. Each cellular channel has a thirty kilohertz bandwidth, allowing for 666 sequentially numbered channels, with channels 1 through 333 being allocated to one service provider and channels 334 through 666 being allocated to the other service provider.
Currently, all channels in a group are available to all subscribers. Under some circumstances, however, it may be desirable to allocate at least some cellular channels to specific users and to ensure that other subscribers not have access to those channels. For example, some commercial customers may wish to use cellular telephone services in their communications and have allocated to them certain of the cellular channels. In addition, it may be desirable to allocate, for at least a brief time while a cellular system is being set up or modified, a set of channels for use by the installation or repair services.